This invention relates to an internal combustion engine and more particularly to a high pressure fuel injection pump drive for such engines.
In order to improve the performance and particularly the fuel economy and exhaust emission control of internal combustion engines it has been proposed to employ direct cylinder injection. Use of such direct cylinder injection has a number of advantages and offers opportunities for significantly improving engine performance. However, the provision of direct cylinder injection requires use of a high pressure pump in order to generate adequate fuel pressure to permit penetration into the combustion chamber, particularly during the compression stroke.
Therefore, it has been generally necessary to employ a high pressure pump which generally is a mechanical pump of the positive displacement type and which must be driven from the engine. This adds considerably to the complexity of the engine construction, bearing in mind the number of other accessories and auxiliaries that are driven by the engine, particularly in automotive practice.
In connection with overhead cam shaft engines, it has been proposed to drive the high pressure fuel injection pump off of one end of one of the cam shafts of the engine. Generally, these ends provide an area that is otherwise unencumbered and also permit the mounting of the high pressure pump in proximity to the fuel injectors.
However, it is necessary to mount the pump in such a way that a driving relationship is accomplished and also so that there is no leakage of oil from the cam shaft chamber to the exterior of the engine in the area where the pump is driven.
The arrangements that have been proposed for this type of drive have disadvantages. First, many of these types of arrangement require end seals on the sealing surface between the pump housing and the cylinder head and cam cover of the engine. Because of these several parting edges, there is a difficulty of ensuring good gasket sealing in this way.
Also, many of the pump drives that have been proposed utilize the cam shaft bearing cap for the engine as a means also to attach the fuel pump housing to the engine. This gives rise to rather bulky constructions which can offset the advantages of compact construction and ease of assembly and servicing.
It is, therefore, a principal object of this invention to provide an improved mounting and sealing arrangement for a high pressure fuel pump drive from the cam shaft of an overhead cam shaft internal combustion engine.
It is a further object of this invention to provide an improved pump mounting structure for the high pressure pump of an internal combustion engine driven off of one of the cam shafts that will provide good sealing as well as a simple and compact construction.